Procedure and equipment for destroying waste by plasma technique

ABSTRACT

Material is comletely atomized, and converted into a plasma state by directing the feeding of the burner so that the material to be decomposed and an oxidizing agent (oxygen, air, etc.,) are in a suitable ratio at every point of the equipment so that the waste transforms in stable combustion products. There is no need for a catalyst or for any other subsidiary materials. The recovery of certain end products as chemical basic materials is also effected. The oxidizing agent may be air, air enriched with oxygen or oxygen. Plasma can be produced from air, or from the waste, itself. With waste materials containing halogens, it is advisable to introduce water into the plasma to promote the formation of hydrogen halogenids. A MHD generators or conventional heat exchangers may be used and the final gases are to be desacidified before letting them outdoors by treatng them with a weak alkaline washing solution.

Subject of the invention: procedure and equipment destroying fluid wastecontaining organic materials.

It is known that reliable destroying of different industrial and wastefrom local communities is a problem causing great anxiety all over theworld, especially in case of poisonous chemical waste. For solving thisproblem various technologies have been developed which proved to besuccessful. Within these, the destroying technologies by burning areexpanding also. As a result of the well-directed burning, the poisonous,infectious, etc., waste decomposes to innocuous end products, even it ispossible to get also energy back from the combustible materials.Moreover, the volume of the originated ashes, slag, etc., is much lessthan the original waste.

The realisation of the burning procedure can be grouped mainly in foursystems including mining furnaces, ovens for central heating, furnaceswith movable beds and those with rotary feeder. The procedures knownuntil now, especially the most developed furnaces with rotary feeder arealready capable to solve many problems but there are still many taskswhich could be solved only by introducing an entirely new process,namely: hydrocarbons of high chlorination degree and similar halogenousproducts cannot be burned or only by means of high capacity auxiliaryburners, the so-called "supporting burners" . Although they are not toosensitive to the composition of the waste, in the interest of thereliable destroying, i.e. in case of violent poisons it is necessary toapply long dwelling period and accordingly, a spacious furnace forobtaining complete burning.

These equipments are operated without exception by hydrocarbon firing,so to run them nowadays is not economical owing to the increasinghydrocarbon prices and to the difficulty of obtaining fuels, inaddition, the situation is getting worse in the future.

The aim of the invention is to establish such a technology which makesthe destroying of such waste possible not only by a reliable manner buteconomically, too.

The procedure of the invention is based on the recognition that in thehigh temperature torch of the high duty industrial plasma flamesatomizes practically every known material completely and gets toplasma-state. If we direct the feeding of the plasma flame so that thematerial to be decomposed and the auxiliary material with an oxidizingeffect--usually air, steam, etc.,--be present in a suitable proportionat every point of the equipment, it is then possible that in therecombination zone of the plasma flame only such ratio of molecules berealised, by which the carbon content of the material fed-in leave thereaction zone in form of aqueous vapour, respectively in H-haloids, itsother elements emerge from it in state of the maximum oxidation. Theworking vapour of the plasma generator can be air, air enriched byoxygen or also the steam of the waste to be destroyed.

An other fact that we recognized is that the plasma-torch wastedestroyer--owing its principle of operation--can be used for every kindof material. For the burning there is no need for a subsidiarymaterial--e.g. for a catalyst--which makes the operation universal andreduces the costs.

On the basis of the above, the substance of the procedure in theinvention is that we produce technical plasma from waste and formit intostable combustion products by introducing extra quantity of oxygen.

We understand technical plasma here to be the state of the material inwhich at least 0.15% of the material-particles are in ionized state andso they are able to perform various technological duties.

The procedure has the advantage that any kind of industrial organicwaste material, especially those having a great halogen content, can bedestroyed--independent of the chemical composition of the material--inan equipment planned for a given capacity and the heat content of theoutgoing end products in vapour form, as well as the individualcomponents (e.g. chlorine gas) can be utilized in the chemical industryby the known methods.

It is advisable to introduce the extra quantity of oxygen necessary forthe procedure in the form of air, as this solution is a more economictechnology both as to investition and to operation costs, as that basedon pure oxygen.

It is advisable, moreover, to enrich the air with oxygen, if thechemical composition of the waste material requires for the completedestroying a relatively greater oxygen proportion as this makes theapplying of a smaller equipment having a less energy demand possible orthe increases of the specific power output of the given equipment.

It is advantageous if for the technical plasma we use plasma from theair, as by this way the oxygen ions necessary for the oxidizing reactionin the high temperature space are being directly at disposal fordestroying the waste material introduced in the plasma-torch. Thissolution means at the same time the more economic realisation of teplasma-formation.

It is advantageous moreover, if the technical plasma will be produceddirectly from the waste, as this is the most rapid, most complete andmost effective method for heating waste to be oxidized to plasma stateassuring the productivity of the technology.

At destroying waste of halogen content, it is advisable tointroduce--besides of oxygen--also water, as during the following gastreatment, the absorbtion of the produced hydrogen haloids is fromtechnological point of view more effective.

We can utilize the energy content of the plasma in an MHD generator. Inthis case by separation of the cactions and anions there is apossibility for a chemical separation, even eventually for a surplusheat production by means of the subsequently chemical reactions.

We can recover the heat content of the gas originating from the plasmaand containing hot combustion products by applying heatexchangers--mainly recuperative or cross flow heat exchangers. In bothcases before guiding them outdoors, we can fix the acid content of theescaping gases by a weak acidic washing solution.

For the executing of the procedure, we use such an equipment which--inthe sense of the invention--has a plasma generator, a reactor to beconnected, as well as feeder armatures introducing fluid waste andoxidizing agent to the plasma generator and/or in the reactor.

We present the invention detailed on the sketch, where we indicated theequipment to be used for the procedure of the invention, as an example.

The outlined equipment serves for destroying chemical waste capable forevaporating--i.e. chlorinated hydrocarbons--in which we apply forestablishing plasma-state air plasma produced by 2 plasma generatoroperated by electric discharge.

The equipment is connected to such further technical equipments whichassure by known manner the introduction of th electric energy-supply,cooling water, compressed air and waster material, as well as of thewashing liquids into the system and provide of draining the warmed upcooling water, the originated outlet water and final gases and eventualof their transformation.

The construction of the equipment is the following: 2 plasma generatorproviding air plasma receives D.C. energy supply by 4 and 6 cables. Forcooling the plasma generator cooling water ca be introduced by 8 pipebranch. Warmed up cooling water discharges through 10 pipe branch.Compressed air, respectively working gas gets through 12 pipe branchinto 2 plasma generator.

2 plasma generator is connected to 14 double-walled plasma reactor ofvertical axe so that 24 plasma torch leaving 2 plasma generator gets inits 26 reaction space on the upper part of 14 plasma reactor. 2 plasmagenerator and 14 plasma reactor are coaxial in case of executionaccording to the example illustrated. Similarly, on the upper part of 14plasma reactor is formed the 16 feeder armature serving for introducingorganic material into the 24 plasma torch. Under the feeder armatureanother feeder armature consisting of 18 gas distributing ring can befound. 14 plasma reactor is equipped with an 20 inner cover, the upperpart of which is a tube with 21 borings for gas intaking or made of gaspermeable ceramics.

The equipment include s also 34 and 36 heat exchangers serving forpreheating the organic material and air introduced into 14 plasmareactor. Cool air gets through 40 pipe branch in 34 which is connectedby 30 pipe branch with 14 double-walled plasma reactor.

Organic material gets in 36 heat exchanger through 42 pipe branch fromwhere it clears away through 28 tubing and gets into 24 plasma torchthrough 16 feeder armature of 14 plasma reactor.

Hot gas leaving 14 plasma reactor gets in 34 heat exchanger through 32tubing, thereafter flows in 36 heat exchanger through 38 connectingpiping. Gas drained from 36 heat exchanger through 44 tubing, gets firstin 46 gas washing appratus, then in 48 gas washing apparatus through 50connecting piping and residual gas discharges of the system through 58tubing. The two gas washing apparatuses should be supplied with washingliquid through 52 pipe branch. Outlet water originating by bindingg thecontaminating gas components can be drained through 54 and 56 pipebranches.

The technological process realised by the outlined equipment can besummarized as follows: 2 plasma generator fed by electric power through4 and 6 cables produces air plasma by heating the compressed air flowingin through 12 pipe branch. Introducing and draining of the cooling waternecessary for operating 2 plasma generator is effected by 8 and 10 pipebranches.

Air plasma flows in the inner part of 14 double-walled plasma reactor.36 heat exchanger heated by hot gases leaving 14 plasma reactorevaporates the fluid organic waste introduced through 42 pipe branch.The vapour gets in 16 feeder armature through 28 tubing which assuresthe introducing of the organic material into 24 plasma torch, as well asits effective mixing. By this the complete dissociation and partialionization of the organic material, respectively its formation intoplasma takes place.

Oxygen necessary for oxidation of the elements of the organic wastematerials is to be introduced in form of preheated air in the inner of14 plasma reactor through 18 gas distributor where in 26 reaction roomthe oxidation processes are proceeding.

Preheating of the air coming in 26 reaction room takes place partiallyin 34 heat exchanger. Air leaving 34 heat exchanger through 30 tubingflows in room between the outer cover made of stainless steel of 14double-walled plasma reactor and 20 inner cover made of heat-and thermalshock resistant ceramics, upwards, i.e. in opposite direction with theplasma-flowing. Part of the streamingg air, still before reaching the 18gas distributing ring gets through 21 bores in the inner part of 20inner cover and along the inner wall of the ceramic pipe it flowsforward according to the flowing direction of the plasma, as a coolinggas layer indicated by 22 arrows. This air quantity--although by mixingwith the plasma it can contribute to the oxidation, too--performs firstthermic and corrosion preventive duties on the most used section of the14 plasma reactor.

End products being in a hot gas state of the plasma-chemical reactionperform--getting through 32 tubing in 34 heat exchanger--preheating ofthe air, then flowing through 38 connecting piping in 36 heat exchanger,the evaporization of the organic waste.

For binding the components of the cooled reaction products delecteriousto the environment, 46 and 48 gas washing equipment series connectedwith 50 piping, serve in which we use a basic washing liquid.Introducing of this takes place through 50 pipe branch. Outlet waterenriched with polluting compounds is drained through 54 and 56 pipebranches.

Gas mixture cleaned from components deleterious to environment, i.e.containing the contaminating compounds in a concentration allowed by thenorms gets in gas washer through 44 tubing and leaves it through 58tubing. In case of necessity, the final gases can be introduced inchimney after having been transformed according to known methods in thechemistry (e.g. drying, heating).

Examples for destroying organic compounds of various composition by theprocedure set forth in the invention:

1. Hydrocarbons: ##EQU1##

It can be seen that in case of increasing the carbon content of thematerial fed in, the ratio of oxygen necessary for the reaction,descreases. In general, the mass ratio of the starting materials will beabout at a value of 3.

2. Compounds containing carbon, hydrogen and oxygen: ##EQU2##

At destroying compounds containing oxygen, the quantity of oxygennecessary for complete burning can significantly decrease and the massratio can get also under 1.

3. Compounds containing carbon, hydrogen and nitrogen: ##EQU3##

In case of nitrogen content, the most extreme variation of the possibleoxidation processes can be characterized by two kinds of reaction. Themaximum ratio of oxygen can surpass 3, but they cannot be higher than3.5.

4. Compounds containing carbon, hydrogen and sulphur: ##EQU4##

In case of compounds containing sulphur there are also more reactionswhich can be imagined depending of the starting ratio of molecules. Massratio of oxygen cannot exceed 3.

5. Compounds containing carbon, hydrogen and halogenid: ##EQU5##

In case of organic halogenids the mass ratio can also be very low; theoxygen requirement is especially small when mainly halogen molecules arebeing formed.

6. At destroying of organic halogenids the aim can be that they shouldbe treated together with the other materials to be destroyed. In such acase it is advantageous, if the gas mixture escaping from theplasma-torch space, contains mostly hydrogen halogenids, e.g.hydrochloric acid, as these products can be absorbed effectively in thewashing liquid. If the hydrogen content of the waste to be destroyed islow, we promote the formation of hydrogen halogenids by feedin of water,as water disintegrates to its elements at the temperature of the plasmaand the hydrogen formed will mainly enter in reaction with the presenthalogen atoms.

    a. 2CHCl.sub.3 +2H.sub.2 +O.sub.2 =2CO.sub.2 +6HCl

    b. CCl.sub.4 +2H.sub.2 O=CO.sub.2 +4HCl

7. On the basis of above examples it can be declared that setting of a4:1 mass ratio of oxygen: waste material is enough to destroy wastepractically of any kind, as it means already in any case a destroying ina surplus quantity of oxygen.

8. If the composition of the waste is known and its destroying requiresrelatively a great surplus of oxygen, it is then advisable to applyduring destroying pure oxygen or air enriched with oxygen, as later asmaller bulk of gas should be treated and the costs of operationdecrease.

Regarding the further characterizing of the procedure, we expound thefollowing:

Plasma torch assuring the reaction space can be formed by simulataneousoperation of two, respectively more plasma-generators. In these casesthe plasma-generators are fitted into the connected reactors so that thewhole volume of the plasma-torches produce a greater and continuousreaction space enabling that waste material particles dwell for a longertime in the high temperature zone by which the wanted decompositionprocess will be completed, at the same time the productivity of thetechnology also increases. By arranging the plasma-generatorscircularly, it is possible to form the so-called "plasma-curtain"through which every particle of the material to be decomposed is forcedto pass. By arranging the plasma-generators staggered, it is possible todirect and influence the individual phases of the planned chemicalreactions.

The plasma reactor can be arranged vertically, horizontally or askew. Atfeeding in of the waste material we can assure e.g. by pulverization ahigh degree dispersion and we introduce the disperged particles by meansof spraying nozzles into the suitable zone of the plasma torch.

The equipment can be transformed--if built of suitable heat- andcorrosion resistant materials--to a completely closed operation type andin this form it corresponds considerably to the regulations ofenvironment protection.

Such a burning equipment requires in comparsion with the traditionalequipments a much smaller place and it can be made eventually in amobile form, too, e.g. similar to a container. Heat inertia of thesystem is small which is advantageous especially when often started andstopped. For its operation electric current is needed which can beproduced and treated easily and economically.

The plasma burner can be utilized not only in independent technologiesbut owing to its 100 % destroying efficacy and universality aspost-burner of the traditional burners, as metioned before, as"supporting burners" too. Operated by such manner it is also ofadvantage that it does not increase the fuel comsumption of thetraditionally burning hydrocarbon.

We claim:
 1. Process for destroying fluid waste containing vaporizableorganic materials comprising the steps of:(a) producing air plasma usingD.C. energy supply generator; (b) transferring said plasma into a plasmatorch at one end of a plasma reactor; (c) introducing organic wastevapor and preheated oxygen into said torch for interaction with saidplasma; and (d) discharging end products of said interaction from theend of said plasma reactor, opposite to the location of said torch, intogas washing equipment.
 2. The process of claim 1 wherein the maximummass ratio of oxygen: waste vapor is 4:1.
 3. The process of claim 1wherein when said waste vapor contains halogen compounds, water vapor isintroduced along with said preheated oxygen.
 4. The process of claim 1wherein the heat content of said end products is used in a heatexchanger to vaporize said organic waster and to preheat said oxygen. 5.The process of claim 1 wherein said preheated oxygen is introduced atthe end of said reactor opposite to the location of said torch and aportion of said oxygen flows through openings in a ceramic pipepositioned coaxially in said reactor, said oxygen portion acting as acooling gas layer and as a corrosion preventive.
 6. The process of claim1 wherein vapors treated in said gas washing equipment are released tothe atmosphere.